1. Field of the Invention
The present invention relates, in general, to variable displacement swash plate type compressors and, more particularly, to a piston-rotation preventing structure for a variable displacement swash plate type compressor that is capable of reducing the size and weight of its piston, thereby reducing the overall outside diameter of the compressor.
2. Description of the Prior Art
In a typical variable displacement swash plate type compressor, a drive shaft is rotatably mounted in the interior of a front housing, a plurality of cylinder bores are formed in a cylinder block that is fixed to the front housing to constitute an entire compressor housing, and the corresponding number of pistons are respectively and reciprocatably received in cylinder bores. Each of such pistons comprises a piston head portion and a jaw portion. The piston head portion sucks and compresses refrigerant gas by its reciprocating movement in a cylinder bore. The jaw portion is formed in the shape of an inverse U in such a way that a horizontal extension is horizontally extended from one side of the upper portion of the piston head portion, inside and outside jaws are respectively and vertically extended from both ends of the horizontal extension, and a recess is defined by the horizontal extension and the inside and outside jaws.
A swash plate is fitted around the drive shaft to be rotated together and the peripheral edge of the swash plate is inserted to the recess of the jaw portion, so that the piston constructed as described above is reciprocated forward and rearward by the rotation of a swash plate. For allowing the swash plate to be rotated without hindrance, two shoe pockets are respectively formed on the inner surfaces of the inside and outside jaws, and two semispherical shoes are respectively inserted into the shoe pockets to hold both surfaces of the peripheral edge of the swash plate. Additionally, a rotating prevention structure is formed on the piston so as to prevent the rotation of the piston due to the rotational resistance of the swash plate while the piston is reciprocated forward and reward.
One of conventional piston-rotation preventing structures for variable displacement swash plate type compressors is disclosed in U.S. Pat. No. 5,706,716. According to the patent, as is seen from FIG. 5, a piston 7 includes two projections 73 formed on both sides of the web 72 of the bridge portion 71 and is inserted into a cylinder bore 91 formed in a cylinder block 9. When the piston 7 receives rotational resistance due to the rotation of a swash plate (not shown) and is about to be rotated while the piston 7 is reciprocated by the rotation of the swash plate, the projections 73 that are projected considerably out of the range of the diameter of the cylinder bore 91 come into contact with the inner surface of the front portion of the housing 10. As a result, the piston is prevented from being rotated.
However, in the conventional piston-rotation preventing structure for a variable displacement swash plate type compressor, since the projections 73 are projected considerably out of the range of the diameter of the cylinder bore 91 or the outside diameter of the piston 7, not only the size and weight of the piston 7 but also the inside and outside diameters of the front portion of the housing 10 is increased.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a piston-rotation preventing structure for a variable displacement swash plate type compressor that is capable of reducing the size and weight of its piston and, consequently, reducing the overall outside diameter of the compressor.
In order to accomplish the above object, the present invention provides a piston-rotation preventing structure for a variable displacement swash plate type compressor, the compressor having a front housing and a cylinder block that constitute the housing of the compressor, the piston having a head portion and a jaw portion, the jaw portion being formed in the shape of an inverse U in such a way that a horizontal extension is horizontally extended from one side of the upper portion of the piston head portion and inside and outside jaws are respectively and vertically extended from both ends of the horizontal extension, comprising a pair of stopper grooves extended along the upper surfaces of the horizontal extension and the piston head portion from the outer edge of the upper surface of the horizontal extension to a certain position on the upper surface of the piston head portion while being spaced apart from each other; and a guide groove longitudinally formed along the inner surface of the front housing over the stopper grooves to have the same width as the space between the stopper grooves.
Preferably, the stopper groove may be situated within the range of the outside diameter of the piston or the inner diameter of the cylinder bore.